reception fades

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reception fades

Post by bill57 on Sun Jan 02, 2011 1:31 pm

Working on a 1951 Zenith G615 that started out with only a hum. Changed two filter caps and got fair reception. Proceeded to change all other paper caps one at a time checked reception as I went. When finished had good clear crisp reception with no background noise. Considered myself done. Then after playing for ten minutes a slight static started and the station would slowly fade away for a couple seconds then come back nice and strong for a few minutes then fade away again. I wiggled all my new connections while playing with no problems. I have checked all the tubes and cleaned all the pins and sockets but could this still be a tube causing this?

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Re: reception fades

Post by Bill Cahill on Sun Jan 02, 2011 9:13 pm

Silver migration in I F cans. Even the 1949 models with the large cans had built in caps that tend to go bad. They can be repaired, but, it's work, and, the transformer has to be taken apart. That's why I won't get late 40's-mid 50's Zenith radios anymore.
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Re: reception fades

Post by bill57 on Sun Jan 02, 2011 9:44 pm

Had a feeling that may be the cause from reading about silver migration. I'll remember that, Bill, if I see any Zeniths from those years. This is the first time I've had this so I'll read up on it and see what I can learn about it.

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Re: reception fades

Post by GaryRabbitt on Tue Jan 25, 2011 3:29 am

bill57 wrote:Had a feeling that may be the cause from reading about silver migration. I'll remember that, Bill, if I see any Zeniths from those years. This is the first time I've had this so I'll read up on it and see what I can learn about it.

HI,
Actually, repairing the cans is no problem. The hardest part it unsoldering the wires from the can to the chassis.

Once you get in side it's easy to disable the built in caps. As those are possibly large cans, you will have lots of room to work with them inside.

For sets that have the smaller 3/4" cans it is simple to disable the caps there too. And you don't need to remove that center rivet from the plastic. A dremel will tunnel in so you can cut the cap connector tabm then slide out the mica.

On both types, you can reinistall a new cap inside the can, or install under the chassis after you reinstall.
Here is a link showing a couple ways to rebuild your cans.
http://www.ppinyot.com/if_transformers.htm

Good luck!
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Re: reception fades

Post by Nick666 on Tue Jan 25, 2011 2:38 pm

Gary,thanks for posting the link to those pics.

Nick
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Re: reception fades

Post by bill57 on Tue Jan 25, 2011 7:19 pm

Thanks for the site, Gary. After seeing that it looks pretty easy. I just may have to dive in and give it a try. I had set the radio back on the shelf till I learned more about it.

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